H, W = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(H)]
E = [[] for _ in range(H * W)]
D = [0] * (H * W)
for h in range(H):
    for w in range(W):
        if h > 0:
            if A[h][w] > A[h - 1][w]:
                E[w + W * (h - 1)].append(w + W * h)
                D[w + W * h] += 1
            if A[h][w] < A[h - 1][w]:
                E[w + W * h].append(w + W * (h - 1))
                D[w + W * (h - 1)] += 1
        if w > 0:
            if A[h][w] > A[h][w - 1]:
                E[w - 1 + W * h].append(w + W * h)
                D[w + W * h] += 1
            if A[h][w] < A[h][w - 1]:
                E[w + W * h].append(w - 1 + W * h)
                D[w - 1 + W * h] += 1

X = [1] * (H * W)
Q = []
for i in range(H * W):
    if D[i] == 0:
        Q.append(i)
while Q:
    a = Q.pop()
    for b in E[a]:
        X[b] = max(X[b],X[a]+1)
        D[b] -= 1
        if D[b] == 0:
            Q.append(b)
print(max(X))